N-(9,11-Dimethoxy-4-oxo-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinolin-3-yl)benzamide

The title schulzeine derivative, C22H24N2O4, crystallizes with two crystallographically independent molecules of almost identical conformation in the asymmetric unit. The tricyclic core of schulzeine has a fused-three-ring system comprising the tetrahydroisoquinoline and delta-lactam moieties. In both molecules, the pyridine ring adopts a twisted-boat conformation, whereas the lactam ring is in a boat conformation. The two methoxy groups are slightly twisted from the attached benzene ring [C-O-C-C torsion angles = -21.3 (2) and -20.5 (2)degrees in molecule A, and -6.3 (2) and -16.2 (2)degrees in molecule B] and the benzamide moiety is in a (-)-synclinal conformation with respect to the lactam ring. In the crystal, molecules are linked into V-shaped dimers by intermolecular N-H center dot center dot center dot O hydrogen bonds and weak C-H center dot center dot center dot O interactions. These dimers are stacked into V-shaped columns along the a axis. Adjacent columns are further linked in an antiparallel manner. C-H center dot center dot center dot pi interactions are also observed.